Prestressed load-bearing beam structure



May 30, 1961 R. W. LESTER PRESTRESSED LOAD-BEARING BEAM STRUCTURE FiledApril 6, 1959 INVENTOR. poberz ZZl Les fer BYZMKC W...

United States Patent ice PRESTRESSED LOAD-BEARIN G BEAM STRUCTURE RobertW. Lester, 277 Bronx River Road, Yonkers, NY. Filed Apr. 6, 1959,v Ser.No. 804,181 7 Claims. (Cl. 189--'37) Load-bearing beams of the generalcharacter under discussion are used to support ceilings, ceilingfixtures, false or hanging ceilings, roofs and the like. These beams maybe embodied in both temporary and permanent installations. For example,they may be used to support false ceilings installed for temporary usein exhibition halls. By the same token, they may be incorporated intopermanent ceilings and roofs of permanent building structures.

The principal object of this invention is the provision of a prestressedstructural beam which combines relatively great structural strength withrelatively light weight. A beam structure of substantially the samedimensions and proportions, made of the same material, but lacking theprestressing feature of the present invention, would sup port far lessweight than a prestressed beam structure of the character hereindescribed and claimed. Moreover, a beam structure which is notprestressed tends to sag and become deformed under a substantial loadapplied to its unsupported portions. A prestressed beam structure asherein disclosed, on the other hand, provides great resistance todeformation under a load. Moreover, such deformation as does take placemerely returns it to the position which it occupied prior to applicationof the prestressing forces. Stated differently, the stress imposed bythe load must first cancel out the stress imposed by the prestressingprocedure before sagging can take place.

An important feature of'this invention is the arch-type structure whichresults from the prestressing action. The structure corresponds to arelatively wide arch whose curvature is almost imperceptible.Nonetheless, it functions in the manner of a true arch in the sense thatit translates the downward force of the load into divided lateral forcesexerted in opposite directions away from each other. This feature leadsto the second object of this invention which is to support theprestressed beam herein claimed on a pair of oppositely disposedvertical sup ports. ,The conventional means for supporting a horizontalbeam is a pair of horizontal supports disposed at opposite ends thereof,spaced a smaller distance apart than the length of the beam which theysupport. In the length of the beam structure in its installed condition.

This feature is not intended to exclude any and all forms ofhorizontalsupport under any' and all conditions. It may be foundnecessary or desirable at certain times and for certainpurposes to'addhorizontal supports-to Patented May 30, 1961 zontal supports would beauxiliary or supplementary. to the vertical supports which are essentialto the proper functioning of this invention.

Another important feature of this invention is the fact that theprestressing procedure is applied at the time of or followinginstallation; it is not performed as a part of the manufacturing orfabricating process. The beam is not prestressed until it is actuallyinstalled and prestressing may be delayed until any predetermined timeor phase of construction following installation.

A further object of this invention is its preloading feature whichsolidifies installation prior to the application of a load. Since thebeam structure which is herein claimed is not inherently prestressed asa separate, independent unit, the process of prestressing must includethe structural supports of the beam. It would be difiicult, perhapsimpossible under certain conditions, to prestress a beam of this typewithout the benefit of the preloading procedure. It is the combinationof the prestressing and preloading aspects of this invention whichprovides it with its greatest advantages.

The invention is illustrated in the accompanying drawing in which: v

Fig. 1 is a side view. of a beam structure made in accordance with thisinvention, showing it installed between a pair of spaced verticalsupports. w Fig. 2 is an enlarged, fragmentary view of one end of saidbeam support, partly broken away, to show the details of one of theprestressing elements.

Fig. 3 is a horizontal section looking downwardly on one of theprestressing supports.

Referring now to the drawing, vertical supports 10 and 12 are intendedto illustrate any suitable supporting elements .such as the oppositewalls of a building or of a room a building or a pair of horizontallyspaced vertical columns or frames in the structural framework of a.building. It is important that these supporting ele: ments be adapted tosupport a load which of course would exert a downward force and alsolateral or horizontal forces exerted leftwardly upon supporting element10 an rightwardly upon supporting element 12. The prestressed beamstructure 14 herein claimed com prises the following component parts: abeamiproper 20, a pair of pressure plates or pads 22 and 24respectively, a. pair of screw-adjustable prestressing members 26 and 28respectively, and a pair of screw-adjustable preloading members 30 and32. respectively.

Turning now to the details of construction of the-illustrated form ofthe invention, it will be understood that beam 20 may be made of anysuitable material and in any suitable shape. For example, it may be madeof structural steel or aluminum, the latter where weight'is a factor.The cross-sectional shape of the beam is not critical and one preferredshape would be rectangular to form a box-type structure. p

By the same token, plates of pads 22 and 24 may be made in any suitableform. and of any suitable material} Steel and aluminum are goodillustrations. These pads are provided preferably, with a pairofvertically extending flanges 40 and 42 respectively which not onlystrengthen and stiffen the pads properbut also serve the means by whichthe prestressing elements are connected to and supported by said pads.The pads maybe secured to the vertical supports 10 and 12 by anysuitable means, such as cement, rivets,- bolts or by simply being placedagainst said vertical supports and held thereby the lateral forces abovementioned I Secured to the beam adjacent each end thereof-ire bracket-44of generally inverted-U shape.- Theyok f 3 each, bracket 44 abuts thebottom wall of the beam and is secured to the beam by means of bolts 46.The adjustable prestressing members 26 and 28 are disposed at theirrespective end portions between flanges 40 and 42 of. the.pressure padsor plates and the corresponding flanges 48 and' 50' of brackets, 44;.More specifically, and referring by wayof illustration. to adjustableprestressing member 26 (the same remarks apply to prestressing'member28) it will be noted that said prestressing member comprises a pair oftubular members 60 and 62 respectively, a thrust screw 64 projecting atits ends into said tubular members, a pair of nuts 66 and 68 threaded onsaid screw in the space between said tubular members, a pair of washers70 and 72 disposed between said'nuts and the adjacent ends of saidtubular members, and a pair of bolts 74 and 76 respectively which attachthe outer ends of said tubular members to flanges 40 and 42 of thepressure pads on the one hand and flanges 48 and 50 of brackets 44 onthe other hand.

Before describing the operation of these prestressing members, it isnecessary to describe the construction, operation' and function of thepreloading members 30 and 32. By way of illustration preloading member30 comprises an eye-bolt 80 and a link 82. The threaded shank of theeye-bolt projects through a hole in the bottom wall of beam 20,immediately adjacent its end, and a nut 84 supports the shank on saidbottom wall. A washer 86 may be interposed between said nut 84 and saidbottom wall of the beam to facilitate the action as will shortly appear.The upper end of link 82 is looped or hooked through the eye of eye-bolt80. The lower end of said link is looped or hookedthrough any one ofseveral holes 88in tubular member 60. Several such holes are formed toprovide for adjustability although only one hole is used at any giventime.

The beam is installed by placing it between a pair of vertical supportssuch as and 11 as shown in Fig. 1. In the event that pressure pads 22and 24 are not firmly secured-to said vertical supports 10 and 12, as bymeans of bolts, but instead are merely held against said verticalsupports, itbecomes necessary'to preload the entire beam structure inorder to provide the necessary lateral or horizontal holding forces.This is done by tightening th'e preloading members 30 and 32 to draw thecorresponding ends of the beam and of the prestressing members closertogether. The prestressing members will of course pivot about theirrespective bolts 76, prestressing member 26 in clockwise direction andprestressing member 28 in counter-clockwise direction. This will createthe necessary outward lateral forces which will jam or wedge theentirebeam structure in place. In effect, the prestressing membars 26 and 28function in the manner of toggle elements between the beam proper andthe pressure pads, thereby setting up the lateral forces necessary to dothe job.

Once the beam structure is securely held in place, the prestressingmembers may be extended in length to provide an upward thrust againstthe beam along their respective axes. This may be done by adjusting therelative positions of nuts 66 and 68 in order to move them fartherapart. This will cause elongation of the prestressing members andprovide the upward thrust forces above mentioned. The result will be tobow the beam in the manner shown in Fig. 1. To the extent necessary,preloading members 30 and 32 may also be tightened following theprestressing operation last described. The beam structure is nowcompletely installed and ready for use.

The-foregoing is illustrative of a preferred form of this invention" andit will be understood that this form may be modified and other forms maybe provided within the broad principles of the invention and the scopeof the claims.

For example, it is not essential that washers 70 and 72 be interposed,as shown, between nuts 66 and 68 on the one hand and tubular members 60and 62 on. the other hand. 'These washers are merely bearings whichprovide a more secure relationship between the nuts and the tubularmembers and also facilitate rotation of said nuts relative to saidtubular members under a load. The same situation obtains with respect towashers 86 which help distribute the force exerted by the preloadingmembers over a larger area of the bottom wall or web of the beam. Thesewashers also facilitate rotation of nuts 84 under a heavy load.Nonetheless, the structure will function without such washers 86. By'the same token, the invention is not limited to the precise shape of thevarious elements shown. By way of illustration, it is not essential thatthe precise screw adjusting means in both the prestressing andpreloading members be used. Other forms of screw adjusting means mayalso be used.

I claim:

1. A beam structure of the character described, comprising a beamadapted to be supported in horizontal position between a pair ofvertically disposed structural supports, a pair of oppositely inclinedprestressing members disposed below said beam and converging at theirupper ends and diverging at their lower ends, said prestressing membersbeing secured at their upper converging ends to said beam inwardly ofits" ends, a pair of vertically disposed pressure pads secured to thelower diverging ends of said prestressing members and adaptedto engagesaid structural supports, and a pair of preloading members secured attheir upper ends to the ends of said beam and at their lower ends to thelower diverging ends of said prestressing members, said prestressingmembers being longitudinally extensible to apply upward forces upon thebeaminwardly of its ends, said preloading members .being longitudinallycontractible to apply downward forces. upon the ends of the beam,whereby the beam may be caused to bow upwardly in prestressed condition.

2. A beam structure in accordance with claim 1, wherein the prestressingmembers are longitudinally adjustable, each said prestressing membercomprising a pair of longitudinally spaced and aligned tubes, a screwbetween said' tubes and projecting at one end into one of said tubes andat the other end into the other of said tubes, and a pair of nuts onsaid screw, one of said nuts engaging one of said tubes and the other ofsaid nuts engaging the other of said' tubes.

3. A beam structure in accordance with claim 2,

wherein vertically extending brackets are providedon the beam and on thepressure pads, the tubes of said prestressing members being pivotallysecured to said brackets for pivotal movement about parallel horizontalaxes. .1 4. A beam structure in accordance with claim 1, wheren thepreloading members each comprise an eye-bolt adustably secured to thebeam and a link adjustably secured to the prestressing member, saideye-bolt and said link being interconnected.

5. A beam structure in accordance with claim 4, wherein the beam isprovided with a bottom wall, each said eye-bolt projecting through saidbottom wall with its threaded shank, the eye projecting downwardly fromsaid bottom wall, and a nut on said threaded shank which engages the topof said bottom wall.

6. A beam structure in accordance with claim 4, wherein. eachprestressing member is provided with a plurality of holes formed thereinadjacent its lower diverging end, the link of the correspondingpreloading member being selectively engageable with said holes.

supports, a pair of pressure pads being adapted to be secured to saidstructural supports adjacent and below the ends of said beam, a pair ofoppositely inclined prestressing members attached at their lower ends tosaid pressure pads and. at their upper ends to said beam inwardly of theends of the beam, and a pair of preloading members secured at theirupper endsto the ends of the beam and; at their lower ends to the lowerends of the prestressing members, said preloading members beingvertically adjustable to draw the ends of the beam and the lower ends ofthe prestressing members toward each other in order to apply horizontalforces to the pressure pads jamming them against the vertically disposedstructural supports and thereby supporting the beam thereon, saidprestressing members being longitudinally extensible to apply upwardforces upon the beam intermediate its ends and thereby causing the beamto bow upwardly in prestressed condition.

References Cited in the file of this patent UNITED STATES PATENTS SelwayDec. 6, 1927 Mechling June 6, 1950 FOREIGN PATENTS Switzerland Mar. 4,1911 Belgium June 23, 1953

